1. Field of the Invention
This invention is related in general to the oral administration of water-soluble medication and nutritional supplements. In particular, it describes a method for optimal intake of vitamin C.
2. Description of the Related Art
Vitamin C, ascorbic acid, has long been known to prevent scurvy and more recently has been shown to have an effect on the healing of wounds, the health of gums, and the strength of bones through the stabilization of collagen. See Davies, M. B. et al., "Vitamin C: Its Chemistry and Biochemistry," Cambridge, Royal Society of Chemistry, 1991, pp. 7-25; Stare, F. J. and I. M. Stare, "Charles Glen King, 1896-1988," J. Nutr., 118:1272-7, 1988; and Roig, M. G. et al., "L-Ascorbic Acid: an Overview," Tnt. J. Food Sci. Nutr., 44:59-72, 1993. However, other possible health benefits, including prevention of cancer (see Roig, supra; Block G., "Vitamin C, Cancer and Aging," Age, 16:55-8, 1993; Marwick, C., "Cancer institute Takes a Look at Ascorbic Acid," JAMA, 264:1926, 1990; and Wittes, R. E., "Vitamin C and Cancer," New Engl. J. Med., 312:178-9, 1985), prevention of heart attacks and reduction of cholesterol (Burr, M. L. et al., "Incidence for Premature Rupture of Membranes in Pregnant Women with Low Leukocyte Levels of Vitamin C," Eur. J Clin. Nutr., 39c:387-8, 1985; Kimura, H. et al., "Dietary Ascorbic Acid Depresses Plasma and Low Density Lipoprotein Lipid Peroxidation in Genetically Scorbutic Rats," J. Nutr., 122:1904-9, 1992; and Uchida, K. et al., "Effect of Vitamin C Depletion on Serum Cholesterol and Lipoprotein Levels in ODS (od/od) Rats Unable to Synthesize Ascorbic Acid," J. Nutr., 120:1140-7, 1990), and as a boost to the immune system to prevent colds (Blanchard, J. et al. "Comparison of Plasma, Mononuclear and Polymorphonuclear Leukocyte Vitamin C Levels in Young and Elderly Women during Depletion and Supplementation," Eur J. Clin Nutr., 43:97-106, 1989; Chavance, M. et al. "Vitamin Status, Immunity and Infections in an Elderly Population," Eur. J. Clin. Nutr., 43:827-35, 1989; Vallance, S., "Platelets, Leukocytes and Buffy Layer Vitamin C After Surgery," Hum. Nutr., 40c:35-41, 1986: and Vojdani, A. and M. Ghoneum, "In Vivo Effect of Ascorbic Acid Enhancement of Human Natural Killer Cell Activity," Nutr. Res., 13:753, 1993), remain controversial.
The "free radical theory of aging" has been postulated to explain age-related cell damage in animals and plants. See Pryor, W. A., "The Formation of Free Radicals and the Consequences of their Reactions in Vivo," Photochem. Photobiol., 28:787-801, 1978; and Harman, D., "The Aging Process," Proc. Natl. Acad. Sci. USA, 78:7124-7128, 1981. Vitamin C appears to play a synergistic role with vitamin E in providing essential anti-oxidant protection (Tappel, A. L., "Vitamin E as the Biological Lipid Antioxidant," Vitam. Horm., 20:493-510, 1962; and Niki E. et al., "Inhibition of Oxidation of Methyl-Linoleate in Solution by Vitamin E and Vitamin C," J. Biol. Chem., 259:4177-4182, 1984). Given the large number of "free radical" diseases, it is reasonable to assume that taking an optimal dose of vitamin C could be extremely beneficial, as suggested by Block, G., supra, and by Harman, D. in "Free Radical Theory of Aging: Current Status," Lipofuscin 1987: State of the Art, edited by I. Zs.-Nagy, New York, Elsevier, 1988, pp. 3-21. With around 20 million people in the U.S. taking daily supplements of Vitamin C, it is appropriate to ask what an optimal dosage would be.
Unfortunately, the optimal dose of vitamin C is not established. The recommended daily allowance sufficient to prevent scurvy varies from 30 mg in the United Kingdom to 60 mg in the U.S. and 90 mg in the former Soviet Union. In contrast, mega-doses of up to 16 g per day are suggested to provide additional health benefits.
In fact, the optimal dose of vitamin C depends on many factors. It is water soluble and cannot be stored in the body to any great extent. However, when vitamin C is regularly ingested, a body pool develops, which may become large even though some vitamin C is being excreted in the urine. Thus, it can take months of ascorbic acid deprivation for the body pool to become depleted to the point where symptoms of scurvy appear. Large-dose intake benefits may be small because of finite absorption from the intestine, limited metabolism by the liver, or excretion by the kidney. For example, it has been reported that only about 60% of a 500 mg dose is normally absorbed into the body of an average person within the first 12 hr after ingestion, while 40% is excreted prior to metabolization (see Olson, J. A., and R. E. Hodges, "The Scientific Basis of the Suggested New RDA Values for Vitamins A and C," Nutr. Today, 20:14-15, 1985). In fact, it has been ascertained that a certain percentage of any dose is always excreted, and that such percentage increases with the dose (see Blanchard, J. et al., "Effects of Age and Intake on Vitamin C Disposition in Females," Eur. J. Clin. Nutr., 44:447-460, 1990).
Without a clear physiological endpoint to measure an optimal dosage or a complete understanding of the functional role of vitamin C, it is unclear how much vitamin C one should take. Because large doses are not entirely absorbed and may even irritate a patient's stomach, and because small doses may be insufficient to provide sufficient anti-oxidant protection, there exists a need to determine a dosage sufficiently large to ensure as large as possible a presence in the body while at the same time minimizing excesses and waste through excretion. This invention provides a method that fulfills this need by ensuring that some excess vitamin C is always present in the urine of a user.